How does the Degree of River Regulation Influence the Impact of Climate Change on Downstream Flow Regimes?

Abstract

The Australian Murray-Darling Basin (MDB) faces increasing competition between economic and environmental water use. This occurs against a backdrop of high climate variability. Here we explore how the impacts on downstream flow regimes (a surrogate for environmental impact) and the response to climate change depend on the degree of river regulation. We have used a water allocation simulation modelling approach to share the available water between these two sectors and to explore the economic and ecological responses. The modelling approach is based on a generic catchment with storage, an irrigation area and a tributary joining between the storage and irrigation area. The storage size and irrigated area are varied to represent different degrees of regulation. The results show that the increase in river regulation results in marked changes in the hydrograph both upstream and downstream of the irrigation area. The impact of climate change was analysed by running the model using stream flows under the ‘Cdry” scenario and testing the reliability of supply to irrigation. The analysis of the results concluded that the reliability of supply to irrigation and environment are severely affected.